Telecommunications equipment is typically designed for indoor temperature controlled environments, but is now frequently deployed in outdoor locations. When telecommunications equipment is deployed in outdoor locations, a cabinet is used to provide environmental protection and to control thermal conditions within the cabinet. The electronic equipment is generally contained in one or more removable card modules that plug into a backplane in the cabinet. The card modules are supported in the cabinet by a subrack and include connectors that mate with corresponding connectors on the backplane. Air flows through the subrack between the card modules to heat and/or cool the electronics on the card modules.
Card modules are usually installed and removed by using) a board extraction tool. The board extraction tool fits into a keyhole in the face panel of the card module and is rotated to engage the card. Once the card is engaged, the card can be pulled from its slot in the subrack without damaging adjacent card modules.
The presence of the keyhole in the card module presents a problem when the switching cabinet is deployed in an outdoor location. Air flow through the subrack leaks through the keyhole into the interior of the cabinet thereby reducing heating and cooling efficiency. The keyhole also allows ambient air to enter the protected space inside the subrack. The ambient air may carry contaminants that could be harmful to the equipment within the cabinet.
Previous solutions to this problem include covering or filling the keyhole with tape or fillers. These solutions are not adequate because they do not allow for a board extracting tool to be inserted into the keyhole for removing the PC board. Replaceable fillers or plugs have also been used which cover the hole and may be removed to insert the board extracting tool. When the filler is removed from the keyhole, the replaceable fillers or plugs are sometimes lost or damaged and, therefore, not placed back into the keyhole. Another drawback of keyhole plugs is they are expensive to manufacture or time consuming to install and remove. Both of these criteria result in the keyhole being left open as the user will chance damage to the PC board because the solution is too expensive or creates too much work and is too aggravating for use.